This invention relates to an apparatus for interfacing input signals of a system with a processor of a programmable controller controlling said system.
In programmable controllers the processor receives input data from the system being controlled via a plurality of input modules arranged on an input rack assembly. The modules are adapted to receive input data from the system indicating the status of the various elements of the system and produce from this data logic signals which are then passed to the processor. The modules also serve to indicate the status of the associated element and to suppress noise.
The input status signals from the system, i.e. inputs from push buttons, limit switches, selector switches, pressure switches, etc., may be of different amplitudes and may be either d.c. or a.c. In such cases it is necessary to identify the characteristics of the signal in a particular channel and provide a compatible input module which is capable of receiving a signal of that characteristic to produce therefrom the required logic signal.
Because of this circumstance, it has been necessary to provide a plurality of different input modules capable of handling the plurality of different input status signal characteristic found in a given system.